19F(p, α)16O and 19F(α,p)22Ne Reaction Rate Measured via THM and Fluorine Nucleosynthesis in AGB stars

Abstract

Asymptotic Giant Branch (AGB) stars have been proven to be sites of F production through spectroscopy observations by several authors, but it is not clear whether these stars might account for the total fluorine abundance of the Galaxy. Recently the two main channels for ¹⁹F destruction in AGB stars, namely the ¹⁹F(α,p)²²Ne and ¹⁹F(p,α)¹⁶O reactions, have been studied via the Trojan Horse Method in the energy range of interest for astrophysics. In both cases experimental results have shown the presence of resonant structures below 500 keV, hinting to an enhancements in efficiency of fluorine destruction by stellar H- and He- burning. In particular the ¹⁹F(p, α)¹⁶O reaction rate at T ₉ ≤ 0.2K turns out to be increased up to a factor of 1.7 while the ¹⁹F(p, α)¹⁶O is enhanced more than a factor of 4 at 0.1 ≤ T ₉ ≤ 0.25. We present here a re-analysis of the role of AGB stars as fluorine galactic source by comparing stellar observations with predictions of AGB nucleosynthesis (for stellar masses from 1.5 to 5M_⊙) computed by employing in state-of-the-art models the THM reaction rates for ¹⁹F destruction.